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971.
The influence of bioturbation on certain aspects of the biogeochemistry of sulfur and iron was examined in shallow-water sediments of Great Bay Estuary, New Hampshire. A bioturbated (JEL) and non-bioturbated (SQUAM) site were compared. Annual sulfate reduction measured with 35S, was 4·5 times more rapid at JEL. A significant portion of this difference was attributed to rapid rates which occurred throughout the upper 12 cm of sediment at JEL due to infaunal reworking activities. Sulfate reduction decreased rapidly with depth at SQUAM. FeS in the upper 2 cm at JEL increased in concentration from 3 to 45 μmol ml−1 from early May to late July while only increasing from 3 to 8 μmol ml−1 at SQUAM. Infaunal irrigation and reworking activities caused rapid and continous subsurface cycling of iron and sulfur at JEL. This maintained dissolved iron concentrations at 160–170 μM throughout the summer despite rapid sulfide production. Therefore, dissolved sulfide never accumulated in JEL pore waters. Although dissolved organic carbon (DOC) was generated during sulfate reduction, bioturbation during summer caused a net removal of DOC from JEL pore waters. Sulfate reduction rates, decomposition stoichiometry and nutrient concentrations were used to calculate turnover times of nutrients in pore waters. Nutrient turnover varied temporally and increased three-to five-fold during bioturbation. A secondary maximum in the abundance of recoverable sulfate-reducing bacteria occurred at 10 cm in JEL sediments only during periods of active bioturbation, demonstrating the influence of macrofaunal activities on bacterial distributions. 相似文献
972.
为了开发新型的脱色填料,进行海绵铁对活性艳红K-2BP的脱色动力学研究。试验结果表明,海绵铁对活性艳红K-2BP具有较高的脱色率,在10min,30min和60min脱色率分别为58.78%,85.2%和93.89%。在海绵铁表面衰减分析的基础上,建立了脱色动力学模型,并研究了pH值、温度、粒径和投加量对反应速度常数K和表面衰减系数Ka的影响。 相似文献
973.
Paul J. Harrison 《Journal of Oceanography》2002,58(2):259-264
The Northeast Pacific has one of the longest time series of any open ocean station, primarily as a result of the weathership
station at Station P from the 1950s to 1981. This review summarizes our understanding of the plankton ecosystem for this station
and examines interannual variability for the primary producers. The weathership era characterized a period of high temporal
sampling resolution with a limited number of parameters being measured. In contrast, the post-weathership period focussed
on seasonal sampling (usually three times per year), but a wider range of parameters were measured and sediment traps were
deployed to estimate carbon and opal flux rates. The mixed layer depth is shallow compared to the Atlantic Ocean, ranging
from 40 to 120 m in late summer and winter respectively. Nitrate, silicate and phosphate are saturating year round with only
a few exceptions in the 1970s. Winter and summer Si:N ratios are the same (1.5:1). Ammonium and urea are 0.5 uM in winter
and near detection limits (∼0.1 uM) in late summer. Iron is limiting (∼0.05 nM) in late spring and summer for the growth of
large diatoms, but iron is co-limiting with irradiance in winter. Chlorophyll and primary productivity are low and show little
seasonal variation (about 2 times). Summer chl is about 20 mg m−2 while primary productivity ranges from 400–850 mg C m−2d−1. The f-ratio of 0.25 does not vary with seasons and indicates that primary productivity is fueled by regenerated nitrogen
(e.g. NH4 and urea). Small cells (<5 um) are normally abundant and they utilize regenerated nitrogen produced by the micrograzers;
they do not appear to be Fe-limited, but rather controlled by the micrograzers. Shipboard carboy experiments indicate that
large diatoms become dominant when iron is added. Therefore top down control is exerted by the micrograzers on the small cells,
while there is bottom up control of the large phytoplankton due to low Fe concentrations.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
974.
As part of a larger program focused on understanding the biogeochemistry of large river plumes, we participated in two expeditions during 2000 to sample the Mississippi River plume. Surface water samples were collected using a trace metal clean towed fish and analyzed for total dissolved Fe, organic Fe complexing ligands and their associated conditional stability constants. The ligands in the river plume have conditional stability constants (log K′FeL between 10.5 and 12.3 with an average of 11.2 and standard deviation of 0.6) very similar to ligands found in the open ocean. Comparison of high flow and low flow regimes indicates that variability in flow may be the main cause of the variability in Fe concentrations in the plume. The organic Fe complexing ligands are in greatest excess during a time of higher flow. These ligands are responsible for maintaining very high (5 nM) Fe concentrations throughout the plume. Due to complexation with these organic ligands, the concentration of Fe remains above the Fe-hydroxide solubility level until a salinity above 35 is reached where there appears to be a sink for Fe in the less productive waters. Therefore, Fe is transported a great distance from the river source and is available for biological utilization in the coastal zone. 相似文献
975.
ZhouWcihua WuYunhua ChenShaoyong YinKedong 《海洋通报(英文版)》2003,5(2):14-21
Concentrations of organic matter, iron and manganese in the deep sea surface sediments in the Nansha Islands sea area, South China Sea are measured, Horizontal and vertical distributions of iron and manganese are discussed. The vertical distribution of iron and manganese in the sediments results from reduction, diffusion, and redeposition of manganese (or iron) oxide and hydroxide in the sediment. There are the maxima of iron and manganese in solid phase in the top of the sediment, which is caused by the penetration of O2 and the upward flux of Mn^2 ( or Fe^2 ). Manganese bacteria play a very important role in the cycle of solid-phase iron and manganese in the ocean environment. Manganese bacteria oxidize Mn^2 ( or Fe^2 ) in dissolved state to Mn^4 ( or Fe^3 ) in oxidized state under the aerobic condition, whereas they reduce iron and manganese in anaerobic conditions. 相似文献
976.
沉积物可溶性Fe^3+、Fe^2+含量变化,是反映氧化还原环境的重要指标之一,海洋沉积物Fe^3+/Fe^2+比值已被应用于海洋地质及油气化探上。可溶性亚铁很容易被氧化,为此我们进行了海洋沉积物可溶铁样保存条件的试验研究。试验结果表明,在10℃以下温度条件保存的海洋沉积物样品其可溶铁Fe^3+/Fe^2+比值在90天内变化甚微。 相似文献
977.
Maria Wlodarska-Kowalczuk Michael A. Kendall Jan Marcin Weslawski Michael Klages Thomas Soltwedel 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):1903-1914
High-latitude seas are mostly covered by multi-year ice, which impacts processes of primary production and sedimentation of organic matter. Because of the warming effect of West Spitsbergen Current (WSC), the waters off West Spitsbergen have only winter ice cover. That is uncommon for such a high latitude and enables to separate effects of multiyear-ice cover from the latitudinal patterns. Macrofauna was sampled off Kongsfjord (79°N) along the depth gradient from 300 to 3000 m. The density, biomass and diversity at shallow sites situated in a canyon were very variable. Biomass was negatively correlated with depth (R=-0.86, p<0.001), and ranged from 61 g ww m−2 (212 m) to 1 g ww m−2 (2025 m). The biomasses were much higher than in the multiyear-ice covered High Arctic at similar depths, while resembling those from temperate and tropical localities. Species richness (expressed by number of species per sample and species–area accumulation curves) decreased with depth. There was no clear depth-related pattern in diversity measures: Hurbert rarefaction, Shannon–Wiener or Pielou. The classic increase of species richness and diversity with depth was not observed. Species richness and diversity of deep-sea macrofauna were much lower in our study than in comparable studies of temperate North Atlantic localities. That is related to geographic isolation of Greenland–Icelandic–Norwegian (GIN) seas from the Atlantic pool of species. 相似文献
978.
本文通过对长江口及邻近陆架区12个站位的柱状沉积物、间隙水和细菌资料分析,指出了研究区沉积物和间隙水中铁的分布特征,并与细菌、地质资料对比研究、从生物地球化学角度对间隙水中铁的来源及其控制因素作了初步探讨。资料研究表明,沉积物中铁主要赋存于细粒沉积物中,腐植酸中铁由河口向陆架减少。间隙水中铁主要来自沉积物中高价铁,在弧菌科(Vibrionaceae)和假单孢菌属(Pseudomonas)细菌的媒介下,参加了沉积物中某些有机物的降解反应,接收了有机物的电子后被还原,其含量和分布主要受控于参加媒介作用的细菌。 相似文献
979.
980.
Maja A. Lazzaretti Kurt W. Hanselmann Helmut Brandl Daniel Span Reinhard Bachofen 《Aquatic Sciences - Research Across Boundaries》1992,54(3-4):285-299
P, Fe, Mn, and S species were analyzed in water samples from the sediment-water interface collected at four seasonally different times during the course of a year at two sampling sites in the southern basin of Lake Lugano (Lago di Lugano). The results reveal the strong influence of the biogeochemical processes in the sediment on the chemical composition of the lake water above. Consumption of oxygen and nitrate under oxic to microoxic conditions in the water column as well as sequential release of reduced manganese and iron under anoxic conditions was observed as a direct or indirect consequence of microbially mediated degradation of organic matter. The seasonal pattern observed for the release and the retainment of dissolved reduced iron and manganese correlates well with the one for dissolved phosphate. Iron, manganese and phosphorus cycling are coupled tightly in these sediments. Both sediment types act as sinks for hydrogen sulfide and sulfate. An inner-sedimentary sulfur cycle is proposed to couple iron, manganese and phosphorus cycling with the degradation of organic matter. Nutrient cycling at the sediment-water interface might thus be driven by a microbially regulated electron pumping mechanism. The results contribute to a better understanding of the role of sediment processes in the lake's internal phosphorus cycle and its seasonal dynamics. 相似文献